I've carried one for the last several years. I bought it initially because I do quite a lot of walking and cycling in remote areas (eg, Pyrenees), I bought the non-GPS version at the time to save money, on the basis that the GPS addition would add marginal benefit, it seemed a lot of money to spend at the time. However, for flying where a fast fix could be critical (ie if you've ditched), I would think that the GPS version is a must.